Replace Dometic 3 wire with Coleman 4??

[Trippy1313]

Has anybody done it? I want to replace my Dometic Digital Thermostat with the Coleman Mach 4 wire thermostat.

I already cant stand the dometic. I hear great reviews of the Coleman but not sure how it would work, if I'm right the coleman takes 4 wires. My Dometic has 3. I'm hopping somebody knows. Or maybe even just a better 3 wire digital Thermostat.

Thanks again all.

[Trippy1313]

Well maybe the Coleman Mach actually has 6 wires? Can anyone confirm?

My Dometic definitely has three. On not really sure how it can work off three quite honestly, but that's all got.

[poohbear]

Originally Posted by Trippy1313

Well maybe the Coleman Mach actually has 6 wires? Can anyone confirm?

My Dometic definitely has three. On not really sure how it can work off three quite honestly, but that's all got.

If not a Heat Pump the Coleman uses 4 wires IF your using a Coleman AC as you can select hi or low fan speeds. I don't know about the Dometic if it can do speed select. If not then just don't use the wire.

[poohbear]

Originally Posted by poohbear

If not a Heat Pump the Coleman uses 4 wires IF your using a Coleman AC as you can select hi or low fan speeds. I don't know about the Dometic if it can do speed select. If not then just don't use the wire.

My bad, 4 wire for AC but I'm not finding wiring diagram .only found 6 wire for AC, heat, 2 speed fan , & 12 volts + & -

[Trippy1313]

Originally Posted by poohbear

My bad, 4 wire for AC but I'm not finding wiring diagram .only found 6 wire for AC, heat, 2 speed fan , & 12 volts + & -

Yeah, and that's what my Dometic has but only 3 wires.

AC, Heat, and Fan, hi/lo. I dont see how it's even possible to control all that with only three wires.... but that's all its got.

[poohbear]

It " communicates " . I used a lot of communicating tstats on high end ac's and they were model/brand specific. Looks like your gonna have to learn to luv that Dometic tstat

[Duke4857]

My Coleman to Coleman exchange had 6 wires. I put in a digatal thermostat here are the pics again. I have a hard time finding previous posts.

[Trippy1313]

Originally Posted by poohbear

It " communicates " . I used a lot of communicating tstats on high end ac's and they were model/brand specific. Looks like your gonna have to learn to luv that Dometic tstat

Ugh. Not what I want to hear. It sucks.

[carloss]

Originally Posted by Trippy1313

Has anybody done it? I want to replace my Dometic Digital Thermostat with the Coleman Mach 4 wire thermostat.

I already cant stand the dometic. I hear great reviews of the Coleman but not sure how it would work, if I'm right the coleman takes 4 wires. My Dometic has 3. I'm hopping somebody knows. Or maybe even just a better 3 wire digital Thermostat.

Thanks again all.

I had the same thermostat and I hated it. I looked into replacing it, even with Nest or Ecobee thermostats. Too much work to get it done, need to add 24V, relays, etc., and they won't start the furnace when only on DC power. Like others said, the Dometic uses one of the wires for communication with the controller on the AC unit. The other two wires are 12V and ground. At the end we opted for the same POS Dometic thermostat, but the one with Bluetooth. Now we don't have to gamble with the thermostat every time it is touched; we don't touch it at all and use the cell phone to control it.

[brettt]

We have been buying Coleman products for over 30 years,never any issues!Have not bought much lately I think we have everything lol!

[Trippy1313]

Originally Posted by carloss

I had the same thermostat and I hated it. I looked into replacing it, even with Nest or Ecobee thermostats. Too much work to get it done, need to add 24V, relays, etc., and they won't start the furnace when only on DC power. Like others said, the Dometic uses one of the wires for communication with the controller on the AC unit. The other two wires are 12V and ground. At the end we opted for the same POS Dometic thermostat, but the one with Bluetooth. Now we don't have to gamble with the thermostat every time it is touched; we don't touch it at all and use the cell phone to control it.

That's ridiculous, I wonder if I could wire in a Coleman to the A/C unit. Like replace the 3-wire harness.... or if the A/C unit will only accept 3 wire applications...

Otherwise I may look into finding whatever bluetooth dometic t-stat you're talking about. It's just so finicky. It's either not recognizing when I push the buttons, or it's too sensitive and just goes through it all.

[Sloop]

I know this thread is a little old but I came across it wondering if anything as came out since last I looked. I have found a way to use any household thermostat with my 3-wire Dometic thermostat in my camper. The 3 wires are positive and negative 12 volts and a comms wire. The Dometic thermostat constantly sends a small 5-volt signal to the control board located near the ac unit. I used a logic analyzer to find each signal and replicate it using an Arduino. (An Arduino is a small microcontroller, almost like a very small computer.) I was able to send different signals to turn in the ac on low or high. I could also turn on the heat or just the fan by itself. But to use any household thermostat requires more modification. Those thermostats require 24v AC. So I used a small 120v to 24v AC transformer for power. The household thermostat sends 24 ac to whatever it's trying to call so I have those wires connected to a relay. The relay will "turn on" when 24 volts is applied. The other end of the relay is isolated and can tell the Arduino to send a signal. that signal goes up to the Dometic control board to turn on the AC or heat or fan depending on what signal is sent. I know this is a lot of information and maybe be confusing. But I made a video trying to explain it if anyone is interested. It is kinda long and boring, but I tried to explain and show how to do this. In my video, I have a Nest thermostat controlling my Dometic AC unit.

https://www.youtube.com/watch?v=L1Hk...annel=Sloopdog

I hope this helps out anybody still wanting to try this and if something is unclear let me know I can try to explain it better.

[poohbear]

Originally Posted by Trippy1313

Has anybody done it? I want to replace my Dometic Digital Thermostat with the Coleman Mach 4 wire thermostat.

I already cant stand the dometic. I hear great reviews of the Coleman but not sure how it would work, if I'm right the coleman takes 4 wires. My Dometic has 3. I'm hopping somebody knows. Or maybe even just a better 3 wire digital Thermostat.

Thanks again all.

Short answer is NO. Dometic uses a digital signal for control ( communicating thermostat ) . MicroAir has a replacement but pricey.
I could do it but I'm a retired AC tech. All the electronic controls would need to be replaced with mechanical relays & imo not worth the trouble

[GABob]

Had a Coleman Mach slider thermostat in my C, and hated it. Several videos on YouTube show folks switching out to a digital unit for better accuracy, so I bought one at Home Depot and wired her in. Only difference is one fan speed, which was no real loss. I now have a thermostat that everyone loves. Best upgrade so far.